This invention relates generally to the field of ink jet printer systems, and in particular to an ink droplet forming mechanism for use in an ink jet printer system.
It is not uncommon for an ink droplet forming mechanism in a continuous ink jet printer system to include a printhead, a plurality of ink supplies in pressurized fluid communication with respective ink discharge nozzles on the printhead, and a controller for ink heaters associated with each ink discharge nozzle. When the controller activates or energizes a heater, a resistive heating element in the heater is heated to in turn heat an ink stream flowing from the associated nozzle. The heated ink then releases an ink droplet, which is used for printing an image pixel on a receiver medium such as a paper sheet.
Since there is usually only one resistive heater element per ink discharge nozzle, failure of the heater element disables the ink droplet forming mechanism. In this connection, however, prior art U.S. Pat. No. 6,019,457 issued Feb. 1, 2000, generally teaches the use of a main resistive heating element and a redundant resistive heater element per ink discharge nozzle in a drop-on-demand bubble ink jet printer. The redundant heating element appears to be activated only when the main heating element fails. This requires, as stated in the patent, a sensing circuit to sense a failure of the main heating element and then activate the redundant heating element.
According to one aspect of the invention, an ink droplet forming mechanism for use in an ink jet printer system comprises:
an ink discharge nozzle for discharging a printing ink;
at least two heating elements activatable individually to heat a printing ink at the nozzle to form an ink droplet; and
a controller connected individually to each heating element for activating at least two heating elements so that should one heating element fail at least one other will heat a printing ink at said nozzle to form an ink droplet.
According to another aspect of the invention, an ink droplet forming method in an ink jet printer system comprises:
discharging a printing ink from an ink discharge nozzle;
including at least two heating elements separately activatable simultaneously to heat a printing ink at the nozzle to form an ink droplet; and
separately activating at least two heating elements to heat a printing ink at the nozzle to form an ink droplet, but should one heating element fail activating at least one other, so that at least one heating element will heat a printing ink at said nozzle to form an ink droplet.